The present invention pertains to a stair elevator and more particularly to the type especially useful for invalids, such elevator being adapted to be supported on a stairway, and including a chair which travels along a track.
In order to furnish background for the several features of the present invention, the stair elevators disclosed in U.S. Pat. Nos. 2,619,195; 2,619,196 and 2,985,257 may be consulted. Like the stair elevator of the present invention, those disclosed in the aforesaid patents include a chair which is operable along a track supported on a stairway, and they generally involve electrical apparatus for effecting and controlling operation of the chair by the invalid or the like. Such prior art systems or schemes have included, inter alia, reversing switches and cam-operated limit switches actuatable at the upper and lower ends of the track so as to control the operation of the driving motor.
It has been found that a troublesome difficulty arises in connection with the operation of limit switches for controlling the driving motor of a stair elevator of the type contemplated. It turns out that any bending or warping of the rails carrying the cam structures which function to actuate the limit micro-switches results in improper functioning of such switches.
Accordingly, it is a primary object of the present invention to overcome the aforesaid difficulty which arises in respect to cam actuation of limit switches.
Another primary object is to provide an improvement in the braking device which operates to stop movement of the chair in the stair elevator whenever a slackening of the drive cable is sensed by a mechanism to be described.
Yet another object of the present invention is to enable operation of a stair elevator under brown-out conditions; that is to say, to permit functioning of the stair elevator even when the supplied voltage, that is, the normal voltage of 110 volts furnished by the utility, has its value significantly reduced.
Another object is to provide a convenient re-set feature in the event that the stair elevator has been stopped by actuation of one of the emergency switches associated with its functioning.
Another object is to provide a suitable interlock means such that only one of the basic relay devices used in the electrical system can be operated at a given time.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.